1. Field of the Invention
The present invention relates to a method of manufacturing hollow flow profiles having optimum aerodynamic configurations in conformance with a commensurate application, about the respective outer skin of which there flows a first work medium during operation, such as hot gas, whereas ducts which are arranged within the interior of the flow profiles are concurrently streamed through by a second work medium, such as compressed air.
2. Discussion of the Prior Art
Hollow flow profiles of that type are used, for instance, in heat exchangers, such as are disclosed in German Laid-open Patent Application No. 29 07 810. Provided in these known heat exchangers is a manifold having two separate compressed air ducts. Conducted through one compressed air duct is the incoming compressed air into the lancet-shaped flow profiles, heated therein by the hot gases and then conveyed in a preheated condition into the other compressed-air duct, through which the preheated air is then conveyed to a consumer, such as, for example, the combustion chamber of a gas turbine engine. In the known heat exchangers, the heat exchanger matrix which is formed by the lancet-shaped flow profiles evidences a configuration which laterally projects in a U-shape from the respective manifold.
Moreover, flow profiles of that type can also be employed, for instance, as the stator vanes or rotor blades of a turbomachine, for example, a gas turbine engine, where in the utilization as a turbine, for example, the applicable blades are streamed about by hot gas and, on the other hand, they can be cooled by means of high pressure air bled from the compressor and directed through passageways located interiorly of the blade.
It has always been rather problematic to provide a method which is adapted for the manufacture of flow profiles of that type so that, on the one hand, the produced flow profile will be highly temperature resistant, and on the other, will possess the requisite, in particular steady state strength properties, to sustain steady high fatigue loads. Another requirement for the flow profiles is the provision of a smooth outer wall in order to obviate aerodynamic turbulences.
Experimentally, flow profiles of that type have been drawn from so-called semi-profiles, in which the respective semi-profiles have been joined back-to-back and secured by means of a longitudinal joint through welding or brazing. The difficulties encountered in processes like these are considerable:
the respective semi lancet-shaped profiles are asymmetrical and, consequently, very difficult to produce through drawing,
the back-to-back jointing of the semi lancet-shaped profiles causes problems in that gaps or offset edges will occur in the respective outer contour which may produce extensive aerodynamic turbulences,
the longitudinal welded or brazed joint resulting from the experimental manufacture of such profiles is continually exposed to the action of hot gas corrosion.
Additionally, in the case of flow profiles which are experimentally manufactured in that manner it is impossible to reshape the ends of such a double profile into a possibly desired circular connection, wherein the profile could be joined, for example, in the previously mentioned heat exchanger, to the central manifold.